Is there any value in competing for .500?
Absolutely, there is. If you're an 81 win team, then 85 wins is within the margin of error. Look at the Orioles this season. 83 wins and they were in the wildcard run until the last week or two.
Doesn't matter if they make the postseason, if they have something to play for, fans will show up in large numbers.
On the other hand a 70 win team is not going to attract very many fans.